The EU has said it is willing to include Russia in discussions with Kiev about a planned trade agreement that sparked the crisis in Ukraine.

European Commission head Jose Manuel Barroso made the offer in a telephone call with President Putin on Friday.

EU officials said the move was "significant" and reflected a "new climate" in the negotiations.

Meanwhile, the US says it is confident that tanks being used by separatists in eastern Ukraine came from Russia.

"Russia will claim these tanks were taken from Ukrainian forces, but no Ukrainian tank units have been operating in that area," a US state department spokesperson told press.

"We are confident that these tanks came from Russia," she added.

The appearance of the tanks, filmed in various towns in the Donetsk region, sparked a row between Kiev and Moscow.

Russia has denied allegations that the tanks had entered Ukraine from its territory.

'Political discussions'

The European Union is due to sign an association accord and free trade pact with Kiev in the next few weeks.

It is the same accord that former President Viktor Yanukovych dropped in November, which led to the protests that culminated in his removal from power and triggered the current crisis.